求助大佬：去年提高D1T1格雷码，交上去有两个点MLE，该怎么处理呢

#include <bits/stdc++.h>
#define ll unsigned long long 
using namespace std;

int n;
ll k;

void dfs(ll x,ll l,ll r,int t){
	ll mid=l+r>>1;
	if(l==mid && r==mid)return;
	if(x<mid){
		printf("%d",t);
		dfs(x,l,mid,0);
	}
	else {
		printf("%d",!t);
		dfs(x,mid+1,r,1);
	}
}

int main(){
	scanf("%d %llu",&n,&k);
	dfs(k,1,pow(2,n),0);
	return 0;
}